Convert // comment marks to /**/ in order to fix FTBS on ia64

https://bugs.gentoo.org/show_bug.cgi?id=447740

Patch written by Kacper Kowalik <xarthisius@gentoo.org>
--- a/tools/h5dump/h5dump_ddl.c
+++ b/tools/h5dump/h5dump_ddl.c
@@ -1341,8 +1341,8 @@ handle_attributes(hid_t fid, const char *attr, void UNUSED * data, int UNUSED pe
     string_dataformat.do_escape = display_escape;
     outputformat = &string_dataformat;
 
-    //attr_name = attr + j + 1;
-	// need to replace escape characters
+    /* attr_name = attr + j + 1; */
+	/* need to replace escape characters */
 	attr_name = h5tools_str_replace(attr + j + 1, "\\/", "/");
 
 
--- a/tools/lib/h5tools_str.c
+++ b/tools/lib/h5tools_str.c
@@ -632,7 +632,7 @@ h5tools_str_indent(h5tools_str_t *str, const h5tool_format_t *info,
         h5tools_str_append(str, "%s", OPT(info->line_indent, ""));
     }
 
-//    ctx->need_prefix = 0;
+      /* ctx->need_prefix = 0; */
 }
 
 /*-------------------------------------------------------------------------